1. Field of the Invention
This invention relates to a flame retardant water-proofing composition and coating transmission member therewith, and, more particularly, to a composition which is flame-retardant for use near subscriber's premises and is sufficiently water-resistant to complete a buried loop waterproof system for communications cable.
2. Description of the Prior Art
It has been an objective in the telecommunications industry to provide underground transmission media for various reasons. One of these, of course, is the aesthetic appeal of the absence of overhead lines. Another is the prevention of discontinuity of service due to fallen trees, windstorms and the like.
Of course, the burial of transmission media poses several problems which must be overcome to make such a system feasible. One of these is the problem of ingress of moisture into the buried cable with accompanying loss in transmission characteristics. In order to overcome this, the cable must be designed to prevent or resist the ingress of moisture.
The trend today is to fill the interstices of the cores of cable and wire with a waterproofing compound. A waterproofing compound is available for filling the interstices of exchange cable, such as is disclosed in U.S. Pat. No. 3,607,487 issued on Dec. 2, 1968 in the names of M. C. Biskeborn, J. P. McCann and R. A. Sabia. The patented composition is comprised of a mixture of petroleum jelly and a crystalline olefin polymer.
The last link in a buried loop plant includes a so-called service wire or cable which extends from a distribution cable to a subscriber's premises or to a pay station. Of course, the hereinbefore-described service cable poses an additional problem. Since the service cable extends to subscriber's premises, it is required that this cable also be flame-retardant. This requires that any waterproofing compound must also be flame-retardant.
While the petrolatum compound commonly used to fill the interstices of cable is water-resistant, it does not appear to offer the flame-retardant characteristics which are required for installation adjacent to subscriber's premises.